U.S. patent number 9,721,747 [Application Number 15/366,660] was granted by the patent office on 2017-08-01 for grid, method of manufacturing the same, and ion beam processing apparatus.
This patent grant is currently assigned to CANON ANELVA CORPORATION. The grantee listed for this patent is CANON ANELVA CORPORATION. Invention is credited to Yukito Nakagawa, Masashi Tsujiyama, Yasushi Yasumatsu.
United States Patent |
9,721,747 |
Tsujiyama , et al. |
August 1, 2017 |
Grid, method of manufacturing the same, and ion beam processing
apparatus
Abstract
A grid of the present invention is a plate-shaped grid provided
with a hole. The grid is formed of a carbon-carbon composite
including carbon fibers arranged in random directions along a
planar direction of the grid, and the hole is formed in the grid so
as to cut off the carbon fibers.
Inventors: |
Tsujiyama; Masashi (Kawasaki,
JP), Nakagawa; Yukito (Kawasaki, JP),
Yasumatsu; Yasushi (Kawasaki, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
CANON ANELVA CORPORATION |
Kawasaki-shi |
N/A |
JP |
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Assignee: |
CANON ANELVA CORPORATION
(Kawasaki-Shi, JP)
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Family
ID: |
56918553 |
Appl.
No.: |
15/366,660 |
Filed: |
December 1, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170084419 A1 |
Mar 23, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/JP2015/005851 |
Nov 25, 2015 |
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Foreign Application Priority Data
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Mar 16, 2015 [JP] |
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2015-052363 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J
37/32422 (20130101); H01J 37/32651 (20130101); H01J
37/04 (20130101); H01J 37/08 (20130101); H01J
27/024 (20130101); H01J 9/14 (20130101); H01J
37/32357 (20130101); H01J 27/16 (20130101); H01J
2237/31701 (20130101); H01J 2237/3174 (20130101); H01J
2237/303 (20130101) |
Current International
Class: |
H01J
9/14 (20060101); H01J 37/08 (20060101); H01J
37/04 (20060101); H01J 27/02 (20060101); H01J
27/16 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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4-180621 |
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Jun 1992 |
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JP |
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2016/147232 |
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Sep 2016 |
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WO |
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Other References
STIC Non patent literature search information on Carbon-carbon
composites is included from Science.gov/science direct. cited by
examiner .
International Search Report in International Application No.
PCT/JP2015/005851 (mailed Dec. 2015). cited by applicant.
|
Primary Examiner: Owens; Douglas W
Assistant Examiner: Sathiraju; Srinivas
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper &
Scinto
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation application of International
Application No. PCT/JP2015/005851, filed Nov. 25, 2015, which
claims the benefit of Japanese Patent Application No. 2015-052363
filed Mar. 16, 2015. The contents of the aforementioned
applications are incorporated herein by reference in their
entireties.
Claims
The invention claimed is:
1. A plate-shaped grid provided with a hole, wherein the grid is
formed of a carbon-carbon composite including carbon fibers
arranged in random directions along a planar direction of the grid,
and the hole is formed in the grid so as to cut off the carbon
fibers.
2. The grid according to claim 1, wherein the carbon fibers
included in the carbon-carbon composite are chopped carbon
fibers.
3. The grid according to claim 1, wherein at least part of the
carbon-carbon composite is coated with a different material from
the carbon-carbon composite.
4. An ion beam processing apparatus comprising: a plasma generating
unit; a processing chamber; and a grid assembly including the grid
according to claim 1 and configured to extract ions from plasma
generated by the plasma generating unit to the processing
chamber.
5. A method of manufacturing a grid comprising: preparing a
plate-shaped carbon-carbon composite including carbon fibers
arranged in random directions along a planar direction of the
carbon-carbon composite; and forming a hole in the carbon-carbon
composite so as to cut off the carbon fibers by using a processing
tool configured to perform cutting by rotary motion.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a grid plate, a method of
manufacturing the same, and an ion beam processing apparatus.
Description of the Related Art
Ion beam processing such as etching and ion implantation has widely
been practiced in manufacturing processes of electronic components
and the like. An ion beam processing apparatus used in this
processing is often equipped with a thin plate (hereinafter
referred to as a grid) including multiple holes used for extracting
ions from plasma. This ion beam processing apparatus performs
processing by irradiating a processing object with ions, which are
originated from the plasma and transformed into beams as a
consequence of passage through the holes in the grid.
Japanese Patent Application Laid-Open No. Hei 4-180621 describes a
particle beam etching apparatus that includes grids. The particle
beam etching apparatus uses the grids in a mesh form, each of which
is formed either from layered films of carbon and silicon or from
carbon fibers.
U.S. Pat. No. 5,548,953 describes a grid that uses a carbon-carbon
composite as its material. The carbon-carbon composite in U.S. Pat.
No. 5,548,953 has a structure in which some filaments of carbon
fibers are bundled into strands that are then arranged in a woven
fabric form and embedded into a carbon matrix (a base material)
provided with multiple holes. As arrangement examples of the carbon
fibers in the woven fabric form, U.S. Pat. No. 5,548,953 discloses
the following examples in which: the carbon fibers are arranged
parallel to three axes offset by 60.degree. from one another (FIG.
7 of U.S. Pat. No. 5,548,953); the carbon fibers are snaked so as
to skirt the holes (FIG. 8 of U.S. Pat. No. 5,548,953); and the
carbon fibers are arranged in a lattice fashion (FIG. 9 of U.S.
Pat. No. 5,548,953).
SUMMARY OF THE INVENTION
The grid described in Japanese Patent Application Laid-Open No. Hei
4-180621 is formed from layered films of carbon and silicon or from
carbon fibers, and does not include a base material. For this
reason, the grid is low in rigidity and has a risk of insufficient
strength when the grid is increased in size to accommodate an
increase in diameter of an ion beam source.
The grid described in U.S. Pat. No. 5,548,953 employs the
carbon-carbon composite as its material. Accordingly, the grid has
high rigidity and has no risk of insufficient strength when the
grid is increased in size to accommodate an increase in diameter of
an ion beam source. However, the holes are formed in the grid
described in U.S. Pat. No. 5,548,953 in such a way as to skirt the
carbon fibers in the woven fabric form which are arranged in the
carbon matrix. For this reason, it is difficult to position the
holes appropriately during the processing thereof and to
manufacture the grid stably.
On the other hand, if no holes are formed in such a way as to skirt
the carbon fibers in the woven fabric form which are arranged in
the carbon matrix unlike U.S. Pat. No. 5,548,953, then it is
necessary to form such holes in the carbon-carbon composite. The
inventors of this application have found out that there is a risk
of causing problems as shown below in this case.
Note that carbon fibers that are knitted regularly in longitudinal
and lateral directions into a woven fabric form will be referred to
as a "crossed member" in this specification. The carbon-carbon
composite using the crossed member is manufactured by impregnating
the crossed member with a carbon-containing raw material for the
matrix such as a thermosetting resin, and then heating and
carbonizing the crossed member. As a consequence, the carbon-carbon
composite using the crossed member includes the carbon fibers which
expand in two directions perpendicular to each other, namely, in
the longitudinal direction and the lateral direction.
FIG. 4 and FIG. 5 are conceptual diagrams showing positional
relations between a carbon fiber and a hole when the hole is formed
in the carbon-carbon composite using the crossed member. FIG. 4 is
the conceptual diagram showing the positional relation when a
carbon fiber 401 is located at the center of a position of
formation of a hole 202. FIG. 5 is the conceptual diagram showing
the positional relation when the carbon fiber 401 is located near
an end portion of the position of formation of the hole 202.
Regarding the carbon-carbon composite using the crossed member
mentioned above, any of the positional relations in FIG. 4 and FIG.
5 is likely to come into being as a result of forming the holes
without conducting specific positioning with respect to the
arrangement of the carbon fibers.
When drilling work is performed by using a drill in the case of
FIG. 4, a drill bit acts in a circumferential direction of the hole
202 (a direction indicated with an arrow A or an arrow A' in FIG.
4). In other words, the acting direction of the drill bit is
perpendicular to a fiber direction of the carbon fiber 401. The
strength of the carbon fiber 401 in the direction perpendicular to
the fiber direction is smaller than the strengths in other
directions. Accordingly, the carbon fiber 401 is cut off relatively
easily in this case.
In the case of FIG. 5, the drill bit acts in the circumferential
direction of the hole 202 (a direction indicated with an arrow B in
FIG. 5). In other words, the acting direction of the drill bit is
parallel to the fiber direction of the carbon fiber 401. The
strength of the carbon fiber 401 in the direction parallel to the
fiber direction is larger than the strengths in other directions.
Accordingly, the carbon fiber 401 is not easily cut off in this
case. The carbon fibers 401 are knitted laterally and
longitudinally in the carbon-carbon composite using the crossed
member. When the carbon-carbon composite using the crossed member
is circularly pierced with the drill bit in rotary motion, the
acting direction of the drill bit coincides with any of the
directions parallel to the fibers in the longitudinal direction and
the lateral direction at every 90.degree.. Accordingly, the
positional relation as shown in FIG. 5 may hold frequently in the
course of processing the carbon-carbon composite using the crossed
member.
FIG. 6 is an enlarged top plan view of a grid 200 after the holes
202 are formed therein. In the case of FIG. 5, the carbon fibers
401 may be left over without being cut off during the piercing. In
this case, jutting portions 601 of the carbon fibers may be formed
on wall surfaces of the holes as shown in FIG. 6. Furthermore, like
a jutting portion 602 in FIG. 6, the jutting carbon fiber may be
bent along the wall surface of the hole 202 due to a cause such as
the drill bit in rotary motion dragging the carbon fiber. It is
difficult to remove the jutting carbon fiber in this state.
Here, another possible solution is to align the fiber direction of
the carbon fibers 401 with a thickness direction of the
carbon-carbon composite as shown in FIG. 7. In this case, the drill
bit acts in the direction perpendicular to the fiber direction at
the time of piercing, so that the carbon fibers 401 can be cut off
relatively easily. Accordingly, the jutting of the carbon fibers
from the wall surfaces of the holes 202 is less likely to occur in
this case. Nevertheless, the effect of rigidity enhancement by use
of the carbon-carbon composite will be reduced since the carbon
fibers are not oriented in a horizontal direction. It is therefore
undesirable to align the fiber direction of the carbon fibers with
the thickness direction.
As a consequence, while the grid is being manufactured by use of
the rigid carbon-carbon composite as its material, the jutting
portions 601 of the carbon fibers may be formed on the wall
surfaces of the holes as shown in FIG. 6 at the time of processing
the holes.
The present invention has been made in view of the aforementioned
technical problems. An object of the present invention is to
provide a grid, which is easy to process and is less likely to
cause formation of jutting portions of carbon fibers on wall
surfaces of holes at the time of processing the holes.
An aspect of the present invention provides a plate-shaped grid
provided with a hole. The grid is formed of a carbon-carbon
composite including carbon fibers arranged in random directions
along a planar direction of the grid, and the hole is formed in the
grid so as to cut off the carbon fibers.
According to the present invention, it is possible to provide a
grid which is easy to process and is less likely to cause formation
of jutting portions of carbon fibers on wall surfaces of holes at
the time of processing the holes.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a structural drawing of an ion beam etching apparatus
which uses a grid according to an embodiment of the present
invention.
FIG. 2 is a structural drawing of the grid according to the
embodiment of the present invention.
FIG. 3 is a flowchart showing a method of manufacturing a grid
using a carbon-carbon composite.
FIG. 4 is a conceptual diagram showing a positional relation when a
carbon fiber is located at the center of a position of formation of
a hole.
FIG. 5 is a conceptual diagram showing a positional relation when
the carbon fiber is located near an end portion of the position of
formation of the hole.
FIG. 6 is an enlarged top plan view of the grid after forming holes
therein.
FIG. 7 is a diagram showing a state in which a fiber direction of
carbon fibers is aligned with a thickness direction of a
carbon-carbon composite.
FIGS. 8A and 8B are a diagram showing a difference in fiber
direction between a crossed member and a chopped member.
FIG. 9 is an enlarged diagram showing fiber directions of the
crossed member.
FIGS. 10A and 10B are a conceptual diagram showing a case of
forming holes in the grid while using the crossed member and the
chopped member.
FIGS 11A to 11D are a first micrograph of a portion near the holes
in the grid which employs the carbon-carbon composite.
FIGS. 12A and 12B are a second micrograph of a portion near the
holes in the grid which employs the carbon-carbon composite.
DESCRIPTION OF THE EMBODIMENTS
An embodiment of the present invention will be described below with
reference to the drawings. It is to be noted, however, that the
present invention is not limited only to this embodiment. In the
drawings to be described below, constituents having the same
functions will be denoted by the same reference numerals and
repeated explanations thereof will be omitted as appropriate.
Embodiment
As an example of an ion beam processing apparatus, FIG. 1 shows a
structural drawing of an ion beam etching apparatus which uses a
grid according to an embodiment of the present invention. An ion
beam etching apparatus 100 includes a plasma generation chamber 102
for generating plasma, and a processing chamber 101 in which
etching processing takes place. As a plasma generating unit for
generating the plasma, a bell jar (a discharge vessel) 104, a gas
introduction unit 105, an antenna 106, and a Faraday shield 118 are
installed in the plasma generation chamber 102. The bell jar 104 is
part of a chamber external wall, which defines a discharge space of
the plasma generation chamber 102 and keeps the inside vacuum. The
gas introduction unit 105 is a portion, into which a processing gas
such as argon (Ar) necessary for generation of the plasma is to be
introduced. The gas introduction unit 105 is connected to a
not-illustrated gas cylinder and the like. The antenna 106 is an
electric power applying unit formed from conductive wiring and the
like, which is used for generating the plasma inside the bell jar
104. The Faraday shield 118 is a lattice-shaped electrode made of a
metal and installed on an inner wall surface of the bell jar 104.
The Faraday shield 118 has a function to homogenize a high
frequency electric field which is radiated from the antenna.
A discharge power supply 112 which supplies high frequency power
(source power) to the antenna 106, a matching unit 107 provided
between the discharge power supply 112 and the antenna 106, and an
electromagnetic coil 108 which generates a magnetic field inside
the bell jar 104 are provided outside the bell jar 104. A
processing gas introduced from the gas introduction unit 105 is
ionized by supplying the high frequency power from the discharge
power supply 112 to the antenna 106 through the matching unit 107,
and the plasma is thus formed inside the plasma generation chamber
102.
The processing chamber 101 includes a neutralizer 113 which
neutralizes ion beams, a substrate holder 110 which is a holding
unit for holding a substrate 111 being a processing object, and an
evacuating pump 103 which evacuates the inside of the plasma
generation chamber 102 and the processing chamber 101 and keeps the
inside vacuum. The substrate holder 110 includes various substrate
fixtures such as a clamp chuck. Meanwhile, the substrate holder 110
may also be provided with a drive mechanism such as a
rotation-revolution mechanism for projecting the incident ion beam
onto the substrate at a given position or a given angle.
A grid assembly 109 provided with holes to extract ions is
installed at a boundary that separates the plasma generation
chamber 102 from the processing chamber 101. The grid assembly 109
includes one or more grids 200. The plasma generated in the plasma
generation chamber 102 is passed through the holes in each grid 200
and extracted to the processing chamber 101, and is then projected
onto the substrate 111. A voltage is applied from a not-illustrated
voltage supply to each grid 200 for the purpose of ion acceleration
and the like.
An operation of ion beam projection by using the ion beam etching
apparatus 100 will be described. First, the processing gas
containing an inert gas such as argon (Ar) is introduced from the
gas introduction unit 105 into the plasma generation chamber 102.
Next, the processing gas inside the plasma generation chamber 102
is ionized by applying the high frequency power from the discharge
power supply 112 to the antenna 106, and the plasma including the
ions is thus generated. The ions included in the plasma generated
in the plasma generation chamber 102 are accelerated by the voltage
applied to each grid 200 when the ions are passed through the holes
provided in the grid assembly 109. In this way, ion beams are
extracted from the plasma generation chamber 102 to the processing
chamber 101. After the extraction into the processing chamber 101,
the ion beams are neutralized by the neutralizer 113. The
neutralized beams are projected onto the substrate 111, and the
etching processing takes place on a surface of the substrate.
When the grid assembly 109 has a structure in which the multiple
grids 200 are stacked on one another as shown in FIG. 1, the grids
200 are preferably arranged such that the positions of the holes
overlap one another when viewed in a direction perpendicular to a
plane of the grid assembly 109. By arranging the holes as described
above, it is possible to extract the ion beams perpendicularly to
and evenly from the grid assembly 109.
Note that in this embodiment, the ion beam etching apparatus is
depicted as an example of the apparatus that applies the present
invention. However, the present invention is also applicable to
other apparatuses. The present invention is also applicable broadly
to ion beam processing apparatuses such as an ion implantation
apparatus and an ion beam sputtering apparatus, which are
configured to generate accelerated particles by extracting ions
from plasma. Meanwhile, besides the ion beam processing
apparatuses, the present invention may be employed in an
application which uses a plate member that includes multiple holes
and requires strength.
FIG. 2 is a structural drawing of the grid according to the
embodiment of the present invention. The grid 200 includes multiple
holes 202 formed in a grid plate 201. The grid plate 201 is a
disc-shaped member made of a carbon-carbon composite as its
material. In this embodiment, the grid plate 201 is formed into a
circular shape. However, this shape can be changed as appropriate
in accordance with the shape of an ion source to which the grid 200
is applied. Each hole 202 is a circular hole formed in the grid
plate 201. Note that the shape of the hole 202 is not limited to
the circular shape, but may be a shape other than the circular
shape such as a polygonal shape and an oval shape.
As described above, the grid assembly 109 is installed inside the
ion beam processing apparatus and the like. Along with an increase
in size of semiconductor substrates in these years, the ion beam
processing apparatuses are growing in size and the grid assembly
109 is also required to be increased in size. The grid assembly 109
may be installed horizontally or obliquely inside the ion beam
processing apparatus. In this case, the grids 200 constituting the
grid assembly 109 may be warped by their own weights, and gaps
between the holes 202 in the respective grids 200 may vary. If the
gaps between the holes 202 in the respective grids 200 vary, then
it is difficult to extract the ion beams perpendicularly and
evenly. This embodiment uses the carbon-carbon composite which is
high in strength and light in weight, and is therefore less likely
to cause such a problem. Moreover, the carbon-carbon composite has
a low linear thermal expansion coefficient, and is therefore less
likely to cause displacements of the holes 202 attributed to
thermal expansion. Furthermore, since the carbon-carbon composite
mainly uses carbon as its raw material, contamination is unlikely
to be problematic in the course of manufacturing electronic
components and the like by using the ion beam processing apparatus.
From the viewpoints mentioned above, it is preferable to employ the
carbon-carbon composite as the material of the grid plates 201.
FIG. 3 is a flowchart showing a method of manufacturing the grid
using the carbon-carbon composite. In step S301, the grid plate 201
to serve as the material of the grid 200 is prepared. A
carbon-carbon composite plate processed into a given thickness and
a given size in accordance with the design of the ion beam etching
apparatus 100 is used for the grid plate 201. While details will be
described later, the carbon-carbon composite used in this step
includes carbon fibers in the form of a chopped member.
In step S302, the multiple holes 202 are formed in the grid plate
201. Performances of the ion beam etching apparatus 100 including
an etching rate, straightness of the beam, and the like vary
depending on the arrangement of the holes 202, hole sizes, and the
like. Accordingly, in the course of processing the grid 200 for the
ion beam processing apparatus, the numerous holes 202 are required
to be formed stably at a predetermined pitch and with predetermined
dimensions. In view of these requirements, in order to form the
holes stably and at low cost, it is preferable to form the holes by
using a device provided with a processing tool such as a drill and
an end mill, which performs cutting by rotary motion. The following
description will be given on the assumption that the holes 202 are
to be formed by using the drill.
Next, the carbon-carbon composite to be employed as the material of
the grid plate 201 will be described. The carbon-carbon composite
is a composite material in which carbon fibers that are reinforcing
members are arranged inside a carbon matrix (a base material) which
is a supporting member. Mechanical strength such as rigidity can be
improved by combining the multiple materials. Particularly, the
strength in the fiber direction of each carbon fiber is further
improved.
As described above, examples of the carbon fibers used for
manufacturing the carbon-carbon composite include the crossed
member and the chopped member. The crossed member is prepared by
knitting bundles of carbon fibers regularly in the longitudinal and
lateral directions into a woven fabric form. The carbon-carbon
composite using the crossed member is manufactured by impregnating
the crossed member with the carbon-containing raw material for the
matrix such as a thermosetting resin, and then heating and
carbonizing the crossed member. As a consequence, the carbon-carbon
composite using the crossed member contains the carbon fibers that
expand in two directions perpendicular to each other, namely, in
the longitudinal direction and the lateral direction.
On the other hand, the chopped member (also referred to as chopped
carbon fibers) is a material containing short fibers prepared by
chopping carbon fibers in filaments into predetermined lengths
(cutting the carbon fibers into small pieces). The carbon-carbon
composite using the chopped member is manufactured by impregnating
the chopped member processed into a mat-like shape with a resin,
and then subjecting the chopped member to a thermal treatment. At
this time, the fibers of the chopped member are not aligned in a
certain direction, but are oriented in random directions in terms
of a two-dimensional direction (a planar direction) or random
directions in terms of a three-dimensional direction. As a
consequence, the carbon-carbon composite using the chopped member
contains the carbon fibers in the random directions in terms of the
planar direction or the three-dimensional direction. Here, the
expression "random directions" means a state in which the carbon
fibers are in a disorganized state as a whole without having a
certain order such as a periodic structure and symmetry. For
example, a state in which there is a region where the carbon fibers
are partially aligned in parallel but there is not the certain
order of the directions of the carbon fibers as a whole, is also
assumed to be included in the state of containing the carbon fibers
in the "random directions".
In this embodiment, the carbon-carbon composite using the chopped
member is employed as the material of the grid 200 instead of that
using the afore-mentioned crossed member. Reasons why the use of
the chopped member is preferable will be described below while
comparing this case with the case of using the crossed member.
As described previously, when the carbon-carbon composite using the
crossed member is employed as the material of each grid 200 for the
ion beam etching apparatus 100, the carbon fibers may jut out from
the holes after the processing. If this grid 200 is applied to the
ion beam etching apparatus 100, abnormal discharge originating from
jutting portions 601 and 602 of the carbon fibers may occur at the
time of operating the ion beam etching apparatus 100. A possible
option to solve this problem is to remove the carbon fibers jutting
out from the holes after the processing of the grid 200. For
example, reprocessing by use of the drill, removal by aging
processing, or the like is presumable. However, such removal
processing is costly. Accordingly, it is difficult to employ the
carbon-carbon composite using the crossed member as the material of
each grid 200 for the ion beam etching apparatus 100.
FIG. 8A is a diagram showing a relation between a hole formed in
the carbon-carbon composite using the crossed member and
arrangement of the carbon fibers. FIG. 8B is a diagram showing a
relation between a hole formed in the carbon-carbon composite using
the chopped member and arrangement of the carbon fibers. Note that
these drawings depict as if there are the carbon fibers only at
portions below the holes for the purpose of omission. In reality,
however, the carbon fibers are arranged likewise entirely around
the holes. In the carbon-carbon composite using the crossed member
as shown in FIG. 8A, the directions of the carbon fibers 401 are
aligned in a vertical direction and a horizontal direction in FIG.
8A. As a consequence, there is a portion on the circumference of
the hole 202, such as a hole lower end 202a, where the carbon
fibers 401 are not easily cut off. For this reason, this case may
cause a first problem of jutting the carbon fibers out from the
wall surfaces of the holes 202.
On the other hand, in the carbon-carbon composite using the chopped
member, the directions of the carbon fibers 401 are random and not
aligned in a certain direction as shown in FIG. 8B. For this
reason, there is not any certain portion on the circumference of
the hole 202 which is not easily cut off. Accordingly, by employing
the carbon-carbon composite using the chopped member, the carbon
fibers are inhibited from jutting out from the wall surfaces of the
holes unlike the case of processing the carbon-carbon composite
using the crossed member as mentioned above.
Next, a second problem in the case where the grid provided with the
holes by using the crossed member of FIG. 8A is employed in the ion
beam processing apparatus will be described by using FIG. 9, FIG.
10A, and FIG. 10B. FIG. 9 is an enlarged diagram showing fiber
directions of the crossed member. FIG. 10A is a conceptual diagram
showing the case of forming the holes in the grid while using the
crossed member. FIG. 10B is a conceptual diagram showing the case
of forming the holes in the grid while using the chopped
member.
In the carbon-carbon composite using the crossed member as shown in
FIG. 8A, the directions of the carbon fibers 401 are aligned in the
vertical direction and the horizontal direction in FIG. 8A. As
shown in FIG. 9, the crossed member has a structure in which
bundles 401a of the carbon fibers in the vertical direction each at
a prescribed width W and bundles 401b of the carbon fibers in the
horizontal direction each at the prescribed width W are woven
together. Accordingly, when a left hole 202b and a right hole 202c
are formed in the grid plate 201 and at a width smaller than the
width W, a portion where the bundle 401a of the carbon fibers in
the vertical direction and the bundle 401b of the carbon fibers in
the horizontal direction are woven together may not be present
between the left hole 202b and the right hole 202c as shown in FIG.
9. At such a position, part of the carbon fibers 401 may come off
in a lump, thereby creating a level difference 402. In this case,
as shown in FIG. 10A, the level difference 402 may occur on part of
a surface at a portion of the grid plate 201 between the left hole
202b and the right hole 202c, which may cause the second problem of
changes in shape of the holes 202 attributed to the level
difference 402.
The second problem will be described. At an outer peripheral
portion other than a right side from the center of the left hole
202b and a left side from the center of the right hole 202c in FIG.
10A, the bundles 401b of the carbon fibers in the horizontal
direction on a first layer remain on the surface and no level
difference occurs therein. On the other hand, the bundle 401b of
the carbon fibers in the horizontal direction on the first layer
located near the space between the right side from the center of
the left hole 202b and the left side from the center of the right
hole 202c in FIG. 10A is cut into bundles 401c and 401d of the
carbon fibers due to formation of the holes. The bundle 401d of the
carbon fibers in the horizontal direction on the first layer, which
is isolated by being cut off by the left hole 202b and the right
hole 202c, comes off in a lump. Hence, the bundle 401a of the
carbon fibers in the vertical direction on a second layer emerges
on the surface. In this way, the level difference 402 comes into
being between a right portion of the circumference of the left hole
202b and a left portion of the circumference of the right hole
202c. The level difference 402 chips off portions near the right
side from the center of the left hole 202b and the left side from
the center of the right hole 202c, and shapes of the holes are
changed, thereby causing the above-mentioned second problem.
In the ion beam processing apparatus, if the shapes of the holes
202 in the grids are changed, the shapes of the ion beams are
distorted. The distortion in shape of the ion beams adversely
affects scatter angles of the ion beams, thereby causing a problem
of deterioration in processing accuracy (such as a shape of an
etched section in the case of the ion beam etching apparatus, and
film thickness distribution of a deposited substance to be
deposited on the substrate in the case of an ion beam film
deposition apparatus).
On the other hand, as shown in FIG. 8B, in the carbon-carbon
composite using the chopped member, the directions of the carbon
fibers 401 are random and are not aligned in a certain direction.
Accordingly, as shown in FIG. 10B, it is less likely that part of
the carbon fibers 401 comes off in a lump at the time of processing
the holes 202. As a consequence, the problem of changes in shape of
the holes 202, which is attributed to the partial chipping off of
the circumferences of the holes 202, is less likely to occur.
Next, a third problem in the case where the grid provided with the
holes by using the crossed member in FIG. 8A is employed in the ion
beam processing apparatus will be described.
When the ion beam processing is performed by using the ion beam
processing apparatus, the processing object scatters from the
substrate and adheres to the grid. In the case of the grid using
the crossed member in FIG. 8A, the grid may cause a third problem
that the processing object having adhered to the grid comes off the
grid and adheres to the substrate. On the other hand, when the grid
using the chopped member in FIG. 8B is employed in the ion beam
processing apparatus, it is possible to solve the third problem
that the processing object having adhered to the grid comes off the
grid and adheres to the substrate.
A reason why the processing object having adhered to the grid does
not come off the grid when the grid using the chopped member in
FIG. 8B is employed in the ion beam processing apparatus, will be
described on the basis of a technical consideration.
In the case of the grid using the crossed member in FIG. 8A, the
directions of the carbon fibers 401 are aligned in the vertical
direction and the horizontal direction in FIG. 8A. Accordingly, an
indented pattern to be formed on the surface of the grid has
regularity and the surface is flat at the same time. The surface
therefore has a small force to retain the adhering object. For this
reason, when the grid using the crossed member in FIG. 8A is
employed in the ion beam processing apparatus, the processing
object having adhered to the grid may come off the grid and adhere
to the substrate. Hence, this grid cannot solve the third
problem.
On the other hand, in the case of the chopped member in FIG. 8B, an
indented pattern to be formed on the surface of the grid has an
irregular shape, and terminal ends of the carbon fibers are
partially exposed. The surface therefore has a large force to
retain the adhering object. For this reason, when the grid using
the chopped member in FIG. 8B is employed in the ion beam
processing apparatus, the processing object having adhered to the
grid is retained by the carbon fibers. Hence, this grid can solve
the third problem.
Prototype Example 1
FIG. 11A to FIG. 11D show first micrographs of portions near the
holes in the grids which employ the carbon-carbon composites. FIG.
11A is the micrograph of the holes in the carbon-carbon composite
using the crossed member. FIG. 11B is an enlarged view of one of
the holes shown in FIG. 11A. The presence of the first problem of
formation of multiple fibrous jutting portions from the wall
surface of the hole can be confirmed particularly with reference to
FIG. 11B.
On the other hand, FIG. 11C is the micrograph of the holes in the
carbon-carbon composite using the chopped member. FIG. 11D is an
enlarged view of one of the holes shown in FIG. 11C. The absence of
fibrous jutting portions like those observed in FIG. 11B can be
confirmed particularly with reference to FIG. 11D. Thus, it is
confirmed that the jutting of the carbon fibers out from the wall
surfaces of the holes can be suppressed by employing the
carbon-carbon composite using the chopped member as the material of
the grid plate.
Prototype Example 2
FIG. 12A and FIG. 12B show second micrographs of portions near the
holes in the grids which employ the carbon-carbon composites. FIG.
12A is the micrograph of the holes in the carbon-carbon composite
using the crossed member. With reference to FIG. 12A, the carbon
fibers on the first layer between the right side from the center of
the hole on the left side and the left side from the center of the
hole on the right side are cut off by the formation of the holes,
and the carbon fibers thereon come off at a lump. As a consequence,
at this position, the carbon fibers on the second layer emerge on
the surface (as a portion at a central part which looks white in
the micrograph in FIG. 12A). Thus, the presence of the second
problem of occurrence of the level difference on the right portion
of the circumference of the hole on the left side and the left
portion of the circumference of the hole on the right side can be
confirmed.
On the other hand, FIG. 12B is the micrograph of the portion near
the holes in the grid employing the carbon-carbon composite using
the chopped member. With reference to FIG. 12B, it was confirmed
that the above-described second problem was absent, and that the
hole shapes of the hole on the left side and the hole on the right
side were not changed (no portion that looks white comes into being
in the case of the micrograph in FIG. 12B).
According to the embodiment and the prototype examples described
above, the grid for ion beam etching apparatus employing the rigid
carbon-carbon composite can be produced by adopting the chopped
member as the material of the carbon fibers. Since the carbon
fibers are randomly arranged, it is not necessary to conduct
positioning of the locations to form the holes with respect to the
positions of the carbon fibers. Moreover, since the carbon fibers
are inhibited from jutting out in the holes, abnormal discharge
that would originate from the jutting portions is suppressed at the
time of operating the ion beam etching apparatus 100. Accordingly,
it is possible to reduce or eliminate the step of removing the
jutting carbon fibers. Due to these reasons, the grid is
manufactured easily and at low cost. Thus, it is possible to
provide the grid which is high in rigidity and easy to process.
Modified Example
At least part of the grid 200 of this embodiment may be coated with
a material which is different from carbon being the main component
of the carbon-carbon composite. For example, it is possible to use
a metal, a carbon coating of vapor grown carbon or glasslike
carbon, or an insulating body as the coating material. By
conducting the coating after the formation of the holes 202, the
jutting of the carbon fibers can be suppressed more reliably.
The grid 200 of this embodiment is applicable not only to the ion
beam etching apparatus shown in FIG. 1, but also to ion beam
processing apparatuses such as an ion beam film deposition
apparatus. Note that a publicly known ion beam film deposition
apparatus is used when the grid 200 of this embodiment is employed
in the ion beam film deposition apparatus.
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